The preferred embodiment relates to a printing or copying system for processing single sheets as well as to a method for controlling such a printing or copying system. In particular, the preferred embodiment relates to printing or copying systems comprising several processing units which successively process fed single sheets. When sequentially processing these single sheets, a distance is required between the single sheets so that the necessary processing steps for a desired processing of each single sheet can be safely performed.
In particular, in high-performance printing or copying systems having printing rates of >100 sheets DIN A4 per minute and printing speeds of up to >1 m/s, a reduction in the printing rate as a result of too great sheet distances results in a lower productivity of the printing or copying system and thus in higher costs. An optimization of the sheet distances to actual smallest possible minimum distances or at least an approximation to the smallest possible minimum distance between two successive single sheets is required in order to enable an optimum utilization of these high-performance printing or copying systems.
From the document WO 99/50715, the processing and transporting of several single sheets through a printing or copying system in groups is known, each of the groups comprising several single sheets, in particular six single sheets. Each of the single sheets assigned to a group is preferably processed with the aid of the printing or copying system using the same processing steps, as a result whereof the temporal distance and/or the spatial distance remains constant between the single sheets of a group so that a small safety distance can be provided between the single sheets of a group.
The processing steps to be performed by the printing system and required for processing a single sheet or several single sheets, are preferably determined by a control unit of the printing or copying system that is designed as a data processing unit during the processing of a print data stream and/or the processing of print job-accompanying data assigned to the print data. These print job-accompanying data can be included in a job ticket, in particular in a standardized form such as the JDF. Such a control unit of the printing or copying system is preferably a print controller known per se, such as, for example, a print controller used by the applicant under the name SRA controller, which interprets the print data and/or the print job-accompanying data. The interpretation of the data preferably takes place with the aid of a parsing operation performed by the print controller. Such a parsing operation is known, for example, from document U.S. Pat. No. 6,917,435 and document DE 100 41 870. Starting out from the known prior art, the feed of single sheets into a printing or copying system is to be optimized in order to better meet at least some of the following requirements:                to achieve a printing rate as high as possible,        the processing of the single sheets in the printing or copying system is to take place in a safe and trouble-free manner, wherein, in particular, paper jams as a result of single sheets having too little distance to one another or of overlapping single sheets is to be avoided, and/or        the sequential processing of single sheets in several processing units arranged one after the other is to take place in a safe and time-optimized manner.        
Regarded as processing units are in particular:                pre-processing devices such as turn-over or rotating devices for turning over or rotating single sheets,        a printing device or several printing devices arranged one after the other, wherein the printing device or the printing devices can each comprise several printing units, and        post-processing devices such as turn-over, rotating, stapling, punching, binding, folding, embossing, reading, enveloping and/or franking units or franking devices; and        further additional devices such as interposers which interpose additional single sheets into the sequence of single sheets fed by the feed unit, i.e. they additionally insert them into the sequence, preferably between two successive single sheets, and which can interpose the single sheets upstream or downstream of a printing device, preferably downstream of the printing device or downstream of at least one post-processing device.        
Both the image generating processes for generating the desired print images on the single sheets as well as the pre- and post-processing processes for processing the single sheets are becoming more and more comprehensive and demanding due to increased requirements on the printing products. In addition, there is the request and the demand to be able to combine devices of different manufacturers in one processing sequence for processing the single sheets. For meeting the increased requirements on the processing sequence, print job-accompanying data, so-called job ticket data, is provided in the prior art, which, in addition to a print data stream or document data stream is exchanged between several software and/or hardware systems. The job ticket data are preferably stored in a separate data file and correspondingly preferably in a job definition format known as JDF. Regarding this job definition format, there exists a corresponding job messaging format, referred to as JMF. An industrial consortium has agreed upon the JDF specification for the exchange of data formats in the printing process, which, at the time of the present patent application, can be downloaded in the version 1.3 of Sep. 30, 2005 via the web page http://www.cip4.org.
For the data exchange between printers as well as between pre- and post-processing units, an industrial consortium has standardized a data interface which is known as UP3I (Universal Printer Pre- and Post-Processing Interface). With the aid of this data interface, the exchange of control data and processing information between printing devices and pre- and post-processing devices combined with these printing devices is defined. Details on this data interface are published on the web page http://www.up3i.org. All documents and publications mentioned are herewith incorporated by reference into the present specification. The methods, systems and measures described in these documents and publications can be advantageously used in connection with the present invention.